Officials have determined the origin of the Shockey Fire was near an area where target shooting takes place in the Shockey Truck Trail area.
No further details about the fire were released as the investigation is still ongoing, said Capt. Mike Mohler.
Firefighters contained the devastating brush fire last week that destroyed or damaged 30 structures and killed one man in San Diego's East County.
The Shockey Fire burned nearly 3,000 acres in total after sparking up on Sept. 23. It also destroyed 11 residences, 14 outbuildings and 11 vehicles, according to CAL Fire.
By Sept. 26, Cal Fire confirmed a total of three firefighters were injured throughout the course of battling the blaze.
Dozens of residents in Boulevard and Jewel Valley homes who were evacuated when the fire sparked Sunday returned to their homes on Tuesday.
A man identified by the county medical examiner as 69-year-old Carson Robinson, was first reported missing from his home in the Tierra del Sol neighborhood. Robinson was later found dead among the ashes.
Neighbors say Robinson chose not to evacuate, and that he took pride in his home which was filled to the brim with nostalgic items.
The fire burned near the Shockey Truck Trail and the Campo Indian Reservation. All roads in the area have been reopened.
A Local Assistance Center with financial assistance, mental and physical care and guidance from local agencies was set up for victims at the Jacumba Library on Old Highway 80. The County said about two dozen governmental and nonprofit organizations can assist residents at the center.
CAL FIRE is asking the public to call our arson hotline at (800)-468-4408 with any information regarding the Shockey fire.